Introduction

Question 1

What is integral dose?

Answer 1

A measure of the total energy absorbed
(deposited) in treated volume
Dose x mass

Question 2

What is the difference in the integral dose for 3DCRT vs IMRT?

Answer 2

imrt beams have a slightly higher quality penumbra that might result in some very subtle differences in the integral dose of IMRT vs. 3D.

Question 3

What is the difference in dose reporting for 3DCRT and IMRT?

Answer 3

3D: ICRU62 - prescribed to a reference point
IMRT: ICRU83 - prescribed to a volume

The reference point
can be blocked by
MLCs or is not inside
an IMRT segment.

For ICRU 83 you want a median dose D50% reported.

There is a higher emphasis on statisitcs

Question 4

What is ICRU83 level 2 dose reporting?

Answer 4

• D50% (D Median) should be 100% of prescribed dose
• Prescriptive value D95%
• Dmean
• Near Minimum D98% (>95% of prescribed dose)
• Near Maximum: D2% (<107 % of prescribed dose)
• Prescribe to a volume not RP

Question 5

What are the modes, advantages and disadvantages of IMRT?

Answer 5

Static modes:
• Step and shoot (MLC in discrete shape)
• Sliding window (MLC in one motion)
Advantages:
• Target coverage
• QOL
• Department efficiency
Disadvantages:
• Increased treatment time
• Integral dose